1. Field of the Invention
The present invention relates to a method of channel coding for a wireless communication system. More particularly, the present invention relates to a method of Dirty Paper Coding (DPC) using nested lattice codes.
2. Description of the Related Art
A broadcast channel is one of the most fundamental entities in multi-user information theory. For the multi-antenna Gaussian broadcast channel, it is known in the art that Dirty Paper Coding (DPC) can achieve the entire capacity region.
One of the biggest stumbling blocks for this channel has been the ‘impracticality’ of DPC. This is for two reasons. First, DPC requires accurate knowledge of the channel state information for all the channels at the transmitter. Second, even with the state known, it is exponentially complex to perform the encoding and decoding process required by existing DPC mechanisms. Thus, many papers have been subsequently published that focus on approximating DPC using other mechanisms such as Tomlinson-Harashima precoding, zero-forcing precoding and Minimum Mean Square Error (MMSE) precoding. However, results for cellular networks have shown that DPC can have large gains over approximate strategies.
In addition, when the channel state is known at the transmitter, it can be shown that DPC can be implemented exactly (without approximations) with a polynomial-time complexity on average. This means that, for slowly fading environments with channel state feedback, DPC might in fact be a low-complexity technique and thus, closer to being practical than previously understood. Hence, it is necessary to devise a low-complexity mechanism for performing DPC.